Creating closed molds using bags (skins) for use in resin infusion of fiberglass reinforced plastic parts is not new. The use of single use and multi-use bags (skins) have been used on a limited basis in the manufacture of fiber reinforcement plastic parts for years. However, the use of single use bags is cost prohibitive from a labor and material standpoint due to the costs associated with having to purchase, fabricate and fit each bag for every part manufactured.
In addition, the lack of the bag's flexibility in being able to conform to difficult geometries make single use bags even more prohibitive. U.S. Pat. No. 6,086,813 to Gruenwald discloses the use of a preformed vacuum bag, but the drawback of this disclosure is in the care that must be taken for the bag to conform to contours, is labor intensive and having to dispose of the waste bag is costly.
U.S. Pat. No. 5,665,301 to Alanko discusses the use of a unitary reusable vacuum bag and the advantages of a reusable bag over single use bags. This patent also makes reference to U.S. Pat. No. 5,316,462 to Seemann and U.S. Pat. No. 5,087,193 to Hebert, wherein both refer to the use of polymers (in this case silicone) to create multi-use reusable bags, but both also have significant drawbacks due to the large amounts of labor requirements in making the bags and in adapting the bag to different geometries associated with the infusion process.
U.S. Pat. No. 6,723,273 to Johnson et al. references the process of creating a bag or skin using a spray process, but in the process, the bag created becomes part of the finished product and is not reusable as in the process of the present invention.
Therefore one object of the present invention is to provide an improved process in significantly reducing labor in the creation of a reusable soft flexible vacuum bag, that improvement being using a sprayable material to form the bag or skin.
Flexible polymer reusable molding systems have historically been manufactured by either:                Cutting of cured sheets of flexible material, and if necessary gluing cut sheet material pieces to make the end product conform to the geometry of the part to be manufactured. Cured sheets are often manufactured by a third party offsite of the eventual usage location, but could in some instances be done on site, manufactured by pouring a liquid polymer into a sheet form allowing the material to cure in the sheet form prior to the cutting and if necessary the gluing process; or        In more recent processes involving the use of a liquid polymer, dispensed by pouring the liquid polymer directly to the geometric surface to, when cured, forms a flexible sheet referenced in the above alternative method. The liquid polymer, consisting of either one or two components, is dispensed to the intended surface and manually spread around and over the surface to form a thin film coat, by using either a spatula, a brush or some other trowel method. Dispensing the liquid polymer directly to create this product surface requires many hours to manually trowel multiple layers of polymer to create the functionality of the sheet material. The application by troweling for spreading the poured liquid polymer to make a film requires multiple coats, each of which must have adequate “cured film thickness” before a successive coat can be applied. The application of a second, third, or more coats prior to the previous coat having achieved an adequate cured film thickness can require hours before a successive coat can be applied causing the entire process to take a day or more to complete. To trowel or spread an application of a successive coat prior to a previous coat reaching adequate cured film thickness would cause the previous filmed coat to tear caused by the dragging of the successive coat over the previous uncured coat. This tearing would be similar to that seen when applying a second coat of paint over a previous coat of paint before the first coat is adequately dried. To trowel or spread an application is very labor intensive and time consuming.        